Info reader fails to find cross-references to anchors

[Eli Zaretskii]

There was one more problem with this in Texinfo 6.0, which seems to be
specific to MS-Windows: find_node_from_tag unconditionally overwrites
the nodelen value of tags for anchors with -1, thus losing the only
indication it has that the tag entry is an anchor.  This caused any
cross-reference to an anchor to fail.

I fixed this in Texinfo 6.0 like this:

-          (*t)->nodelen = -1;
+         /* NODELEN zero means this is an anchor, so this value
+            doesn't need to be adjusted, and we shouldn't lose it, as
+            it's the only indication of an anchor. */
+         if ((*t)->nodelen != 0)
+           (*t)->nodelen = -1;

The current trunk introduced a cache, and does that for the cached
entry, but I believe a similar change is still due, i.e. n->nodelen
should only be set to -1 for non-anchor tag entries.